Process for making tetraethyl lead



April 14, 1953 SHAPIRQ ETAL 2,635,106

PROCESS FOR MAKING TETRAETHYLLEAD Filed 25, 1951 PER CENT YIELD OF TETRAETHYLLEAD CATALYZ ED NON-CATALYZED o lo 3o so so so I00 REACTION TEMPERATURE c INVENTORS HYMIN SHAPIRO BY EARL G. DE WlTT Patented Apr. 14, 1953 f: FerndalepMiclngfiassignors to Ethyl Corpora- :tion,:New-'Y ork, N. Y., a corporation ofDelaware 1 a 'This invention relates tozani improved "process ion making 'tetr'aethyllead.

At presenttetraeth-yllead'is made commercially byreacting mono's'odiumlead' alloy -'withl ethyl chloride according to the following equation:

1 .4NaPb-l-4CaH clfGzHshPb4NaCl F3Pb The yield of-ztetraethyllead' on-the alkali metal or sodium is around 88 per: cent." .Much effort and;expenses-has beemmade by many previous workers in this-field mim mvexms yield. without changing the entire character .ot the process, but little success has been": achieved, It should bevnoted-that three; atoms of .metallic lead are formed which canbe :iurther treated in a separate and* diflfer'ent process to p'ro-duce tetraeti'iyllead, or reallo'yed with sodium: :L'I-hus even though higher yields en'a lead basis cair be obtained by further treatment of the free lead produced, this does notsolve the problem of obtainixigihigher'yields on-the a1kali metaL' Any loss in sodiumeiiectiveness'is wasted since'the sodium values" which do not produce 'tetraethyllead cannot 1 be recovered economically,- whereas the load can be-recovered readily' and reused. Further', s'uchwasteful'use of sodium also consumes ethyl chloride whichresultsin theformation of useless hydrocarbon icy-products. Thus," this defect in'the past present comm-erciah'pro'cess could stand improvement from the viewpoint of economics. [It isytherefore, among the objects of this-*ln vention to provide a process'for substantially improving the "yields of tetraethyllead basedon the alkali metal used. A further'xobject is" to make 'tetraethyllead in high yields at lower. temperatures and pressures and with less ex?- pensive equipment.

Wehave made the surprising discovery that this -'ohjectcanbe accomplished by treating a ternarylalloy of lead, sodium and potassiumwith ethyl chloride in the presence or a catalyst.

By 'this process we are able to increasef'the yield of tetraethy-llead based on the alkali metal from- 88 to ashigh a's 98= per cent, a figure never before envisioned as attainable in this art.

- Previously; many unsuccessful ""effort's-"have been'm'ade to flnd a catalyst to increase the-ultimate" yield of tetraethyllead from "NaPb alloy above the level of 88* per "cent normally-reached commercially" under optimum "reaction conditions-.'-"Some' organic compounds" have been .found which increase the rate of this alkylation reactionjbut they do not raise"theultimate'yield. Ingeneral; rate accelerators-or this nature are 14. GIB'imSt- (Cl. 260-437) 2 described ln Patents ,Nos. 2,426,598;- =2,464,397;

2;464,298}J2,464,399 and 2,477,465. It should beemphasized that while they accelerate the alkylation reaction, they have no'noticeableeftect' upon the ultimate yield. Indeed, at temperatures-below about 70 C., it was known that these compounds actually reduced the desired yields of tetraethyllead, in somecasesby as'much as 5 per cent or more.

@In lieu ofNaPb alloy in the reaction just-referred to, ithas been suggested that ternary alloys: containing potassium, sodium and lead might loe-iused. 'In this-connection, see U;v S. Bat'entsiNos, 1;668,021'.and 1,749,567. The 'use I of such ternary alloys was believed to increase theyield (lithe-desired tetraethyllead at lower temperatures .above that which would I be obtainedunder the same conditions with. anxNaPb alloys -Fromthe experience of those :familiar with this' field inwthe zuse of accelerator'stfor the"reactionzemployingNaPb alloy, it wasgenerallybelieved that theyv would exert a similar, depressing efiect ifemployed with the ternary alloys. 7 In other'words, itwas assumed that such accelerators would 'deterimentally affect the desiredlultimate l-yields. A's 1a result; investigators in this field'- carefully refrained from employing accelerators in the reaction involvin the potassi'um, sodium and-- lead alloy. Ihis is'apparent .from -a oareful consideration of the-foregoing and other'prior art patents.

mentioned previously, potassium was added iii-small amounts to asodium-lead alloy for'production of-tetraethyllead, but the alkylation was conducted at low temperatures, i. e; 12 to 45 C., and: mum absence of a catalyst, and at lon reaction' time's of at "least 6 hours" and usuallyaround 24= hours. Even at these long reaction times the maximum yield. obtained by such workers wasonly 85 per cent,' which lower-than the: yield obtained in the presentcommercial process. Such workers taughtthat low tempera-' tureswere desirable and that 'high "temperatures were to" tie-avoided. In confirmation of thisgwe have round. that when rthetem'pe'rature is raised to 80 C. in the absence of a catalyst, the yield is only about 40 percent;

: :TheLearlier workers in this field were quite glustifled in operating at low temperatures .1 The optimumyields fromthe 'familiarsodiumlead alloy,.=NaPb, "are obtained attemperatures of about'7-0. to 100 C. (depending on-the other eonditions of reaction);and when the temperature is "raised much over 100 the yields fall oiT greatly owing to increasedside reactions Now," potas sium is considered by chemists to be more active than sodium, and prior workers properly reasoned that optimum temperatures for a ternary alloy containing potassium should be lower than for an alloy containing no potassium. They had no reason to suspect that higher temperatures would produce beneficial results, with or without a catalyst.

Not only did prior workers consider higher temperatures unnecessary, but, on. the contrary, they deliberately sought to avoid them. They were seeking a low temperature process which did not involve expensive pressure equipment, and also they were not inclined to use a high reaction temperature on alloys containing a metal more reactive than sodium because these alkali metal-lead alloys are inherently dangerous.

Further it has been the experience of workers in this field that the addition of other reducing metals to the inter-metallic compound,

NaPb, modifies its homogenous crystal lattice, and that on alkylation at normal operating temperatures of around 80 C. the resulting yield of tetraethyllead based on the total reducing metal content is actually lower than that obtained. with the sodium-lead alloy alone. For example the best yield obtained when about one per cent of magnesium, calcium or sodium itself were added to the sodium-lead alloy, NaPb, was 64, 69, and 84 per cent respectively, underconditions where the yield from NaPb was 88 per cent. However, the yield from NaPb plus one per cent potassium under the same conditions was 92 per cent.

The findings of our invention are in surpris-' ing contrast to these prior results. This is in part shown by the data in Table I and in the figure, giving the tetraethyllead yield versus the reaction temperature for standard NaPb alloy and for our .sodium-potassium-lead alloy, each with and without a catalyst. First, it is evident that the presence of a catalyst has a profound effect on the yield from our alloy, both at elevated and very low temperatures. This involves more thana mere increase in rate of alkylation, for at 80 C. the initial rate for the catalyzed reaction of our alloy is actually lower than that for NaPb, although both reactions go to completion in about the same time and the ultimate yield of tetraethyllead is considerably higher for our alloy. Moreover, as shown by the datain Table II, many of the organic compounds found to be effective catalysts for our reaction are different from those known to increase the rate of alkylation of NaPb. Second, it is evident that with a potassium alloy, the presence of a catalyst is never detrimental; on. the contrary, it increases the yield of tetraethyllead over the entire temperature range. Third, the yield from our alloy with catalyst does not fall off at elevated temperatures as would have been expected, a fact of importance for commercial operation wherein the use of moderately high temperatures facilitates the removal of the heat of reaction.

To obtain the data given in Table I, a series of runs was made in which the conditions were the same except for the temperature and use of catalyst, said conditions being two hours reaction time, theories of ethyl chloride (a theory being the amount of ethylchloride required to react with the alkali metal according to the above equation), and sufficient pressure to maintain the ethyl chloride in liquidphase at the reaction temperature employed. For the catalyzed test 0.2 per cent of acetone was used, based on the alloy charged.

The data so obtained are plotted on the figure, curves A and B being respectively catalyzed and non-catalyzed tests using the present commercial alloy, which consists of one atom of sodium to one atom of lead. It should be noted that in commercial practice curves A and B show that little difference in tetraethyllead yield is obtained at 60 0., and higher, between a catalyzed and a non-catalyzed reaction. On the other hand, at temperatures below 60 C. the non-catalyzed yield is higher than the catalyzed yield.

However, this is not the case for a sodiumlead alloy containing a small amount of potassium. Curves C and D represent the data we obtained when operating with an alloy, containing 1.5 weight per cent potassium, in which the atom ratio of total alkali metal to lead is 1 to 1, curve C being the results obtained on a catalyzed reaction and curve D the results obtained on a non-catalyzed reaction. It is to be specifically noted that, not only is the catalyzed yield higher than the non-catalyzed throughout the temperature range as contrasted with curves B and A for the standard sodium-lead alloy, but at temperatures below 40 C. and above 60 C. the improvement between the catalytic and noncatalytic yield is remarkable, entirely unexpected, and could not be predicted.

We believe that our high yields are realized because the conditions weuse reduce the side reactions obtained previously and therefore permit a higher utilization of the reducing metals. In the present commercial process about 10 per cent of side reactions occur according to the with ethane and ethylene obtained as by-products together with butane. This explains the hydrocarbon gases formed along with most lead ethylation reactions.

To support our belief that our yields are obtained at the expense of by-product formation, three different alloys containing 50'atom per cent lead and 50 atom per cent of alkali metal in which the weight per cent of potassium was 0, 1.25 and 1.5 were reacted for 2 hours at C. with 7 theories of ethyl chloride in the presence of 0.2 weight per cent based on the alloy charged of anacetone catalyst. The yields of tetraethyllead based on the alkali metal were 89, 96, and 98 per cent respectively. Upon completion of the reaction and after removal of the tetraethyllead, the remainder of the reaction mass from each was analyzed for inorganic chloride. Based on such analysis the amount of ethyl chloride consumed in excess of that required to produce the tetraethyllead found, was 8.5, 2.0 and 1.0 per cent respectively. Thus it can be said that the byproduct formation for the present commercial alloy is four to eight times that for our alloy.

Similarly when a sodium-lead alloy containing 1.5 weight per cent potassium was tested at a reaction temperature of 80 (3., in the absence of a catalyst, the by-product formation as measured by above method was 8.5 times that obtained when using an acetone catalyst. Thus even using longer reaction times the non-catalytic yield can never reach the catalytic due to by-product formation.

Thus it is unescapable that the nature of our ca al men i s r al different fr m an v ass 6,106-

df' the prior teachingsrandit: issurpri'sing indeed that. the alloy of our invention, when. ethylated. at. temperatures. between and 100 .,C., and in the presence of acatalyst and .even at relatively short reaction periods, could produce' such amazingly and almost theoretical yields,.i. e. as high as 98 per cent.

Our invention can be best understood by referring to the following working: examples. in. which, unless otherwise. noted, parts and percentages are by weight. and the yield of tetraethyl'lead'is' based onthe amount of alkali metal charged.

To a suitable pressure reaction vessel equipped with cooling, and heating means, charging means, and. pressure release means: were placed 10.0v parts of a ternary alloy containing equiatomic proportions. of lead and alkali metals and in which the potassium content. was 1 .5 per cent. To this was; added 219.3. parts (7 theories) of ethyl chloride and 0.2 weight per cent or parts of acetone based on alloy charged. The reaction Was'conducted forZ hours at 80 C. and a .pressure of 80.poun.ds per square inch. "At the end of this period the. tetraethyllead was separated from the other -re action products and was found to be 33.8 parts. or 97 per. cent yield.

Good results are obtained. for potassium. Weight percentages between 0.1-and 5.0. This is illustrated by the following operations conducted under the same conditions as for Example I. but inv which the potassium content was 0.1,. 0.5, 1.0, 2;!) and 3.0 per cent and in. which the yield of tetraethyllead was 91, 92, 95.5, 95 and.92.5' per. cent respectively. Thus over the entire range of our alloy composition the yield of tetraethyllead is higher than the present commercial operation and higher than that found previously. However for best yields a potassium content in the range between 1 and 2 per cent is preferred.

. vIn the present commercial operationthe yield of tetraethyllead falls off considerably if the con tent of sodium varies from 50 atom per cent. Thus the composition of the alloy is quite critical. Thisis not true to such a large extent when the amount of potassium taught. herein is used. For our alloy within the range of 48: to. '52.. atom percent for the total alkali metal content, the yield of tetraethyllead is always substantially I above 90 per cent. and good yields are obtained outside of this range. For example when the potassium content of three different alloys was kept. constant at one weight per cent but the total alkali metal content was 49, 50 and 52 atom per cent, all. other conditions being the same as for Example I, the tetraethyllead yield was 93, Stand 91 per cent respectively, whereas when thesame tests were repeated with an alloy containing-no potassium the yield was always less than 90 per cent and at 53 atom per cent the yield dropped to 84 percent. Likewisev when the above three alloys containing potassium were employed at a 100 reaction temperature the yields were 94, 95 and 93 per cent respectively. However, it should be noted that the highest yields. are obtained when the atomic ratio of alkali metal to lead-is near 1 to 1. Also the sodium content should be between and 35; Weight per cent. s i

To obtain the advantage of our discovery the temperature range employed should be between 0 and 100? C. and preferably above 60 C. In other tests similar to Example Ithe. catalyzed and non-catalyzed tetraethyllead yields for dif- Table I Percent Tetraethyllead Based on Alkali Metal in the Alley Charged Temperature Catalyst (Acetone) No Catalyst NaPb NaPb+l.5'7 Alloy K. o

Likewise the reaction time can be varied within 4; toil,- hours and high yields obtained. For ex.- ample when using the same alloy and the same conditions as in Example I except that reaction times of /3 hour, 1 hour, 3 hours and 6 hours were used, tetraethyllead yields of 95, 97, 96 and 93 respectively were obtained.

The'amount of ethylating agent is not critical as long as it is used in an amount in excess over the.- stoichiometric requirement. Amounts between 1.0 5 and, 30 theories can be successfully employed although we prefer to use an amount between. 1.2 and 10 theories. Likewise the pressure is not critical but must be sufficient to maintain the ethylating agent in the liquid phase.

As mentioned previously a catalyst is essential to our invention. For example when the acetone catalyst of Example I was left out, theyield of tetraethyllead was only 37 per cent and the non-. catalytic yield never reaches the yield obtainable with a catalyst. For a given temperature the non-catalytic yield may be improved at long reaction times, say 24 hours, unless excessive byproduct. formation prevents it, but such reaction times are impractical and would not be used commercially.

Catalysts other than acetone can be successfully employed in our invention. In general any of the compounds described asrate accelerators in Patents 2,426,598, 2,464,397, 2,464,298, 2,464,399 and 2,477,465 can be used. Othercompounds, diiferent from these in type, can also be used, for example, alcohols, ethers, aldehydes, amines, nitriles and peroxides, most of which are not even rate accelerators for the standard NaPb alloy and none improve the yield on such alloy to any extent, although all of them improve the yield on our potassium alloy.

Our catalysts are organic compounds soluble. in ethyl chloride, containing a CO, a CN or a CS bond, having a boiling point range between -25 C. and 300 0., having a molecular weight between 30 and 250, having a density of less than 1.6, and having a hydrocarbon radical selected from the class of aliphatics and aromatics; in which the number of carbon atoms is less than 15.

Among the catalysts which may be. used for our invention are ketones including acetone, chloroacetone, acetophenone, benzophenone, cy-' clohexanone, diethylketone, methylethylketone, methylisopropylketone, dibutylketone, and phen--. ylethylketone; esters including ethyl acetate, ethyl formate, vinyl acetate, diethyl carbonate, ethyl propionate, methyl acetate, dibutyl carbonate,, ethyl acrylate, ethyl crotonate, benzyl acetate and ethyl benzcate;'alcohols including ethyl loco monsoon W alcohol, methyl alcohol, capryl alcohol, benzyl alcohol, isopropyl alcohol, isobutyl alcohol, butyl alcohol, amyl alcohol, phenylethyl alcohol, and phenylpropyl alcohol; ethers such as allyl ether, propylene oxide, phenylethylene oxide, and 1,2- dimethoxyethane; aldehydes including isobutyraldehyde, benzaldehyde, furfuraldehyde, propionaldehyde, acetaldehyde and isoamylaldehyde; amines including isopropylamine, pyridine, triethylamine, methylamine, butylamine, isobutylamine, amylamine, diethylamine, and diisopropylamine'; amides including butyramide, isobutyramide, phthalimide and acetanilide; nitriles including propionitrile, acrylonitrile, acetonitrile, butyrylnitrile and isobutyrylnitrile; anhydrides including butyric anhydride, benzoi'c anhydride, phthalic anhydride, acetic anhydride, propionic anhydride, and isobutyric anhydride; acetals including methylal (dimethoxymetha'ne), ethylal (1,1-diethoxyethane) methoxyethane, 1,1-dimethoxypropane, and 1,1- dipropoxyethane; peroxides including ditertiarybutyl peroxide, isooctyl hydroperoxide, and benzoyl peroxide; aliphatic and aromatic nitro compounds such as nitroethane, nitrobenzene, nitropropane, nitromethane, nitrobutane, nitropentane anddinitrobenzene; esters of nitric and nitrous acids such as ethyl nitrite, amyl nitrate, isopropyl nitrite, benzyl nitrite, isoamyl nitrate, ethyl nitrate, butyl nitrate, propyl nitrate, and benzyl nitrate; acyl and aroyl halides including propionyl chloride, propionyl bromide, propionyl iodide, butyryl chloride, benzoyl chloride, and benzoyl iodide; isocyanates and isothiocyanates including phenylisocyanate and phenylisothiocyanate.

To illustrate the successful employment of our catalysts, tests were made identical to Example I with the results shown in the following Table II.

Table II Tetraethyllead Yield 7 Weight With Catalyst, percent Without Catalyst, percent Acetone Chloroacetone. Acetophenone.

Benzophenone. Cyclohexanone Ethyl Acetate Ethyl Formate... Vinyl Acetate... Diethyl Carbonat Ethyl A1cohol. Methyl Alcohol. Capryl Alcohol... Benzyl Alcohol... Allyl Ether Propylene Oxide Phenylethylene Oxide Dimethoxycthane 1,2. Isobutyraldehyde Benzaldchyde Furfuraldehyde... Isopropylamine. Acetanilide.... Propionitrile Butyric Anhydride Benzoic Anhydride Phthalic Anhydridc Methylal (dimethoxymcthane). Ethylal (Ll-diethoxyethane) Ditertiarybutyl Peroxide Nitrobenzene Ethyl Nitrite Isoamyl Nitrate... Propionyl Chloride.

Phenyl lsocyanate.

Aluminum Chloride I The amount of catalyst employed generally diethoxymethane, 1,1-ditemperature and the ratio of reactants, although substantial yields are obtained when the concentration of catalyst varies from the optimum within the above limits.

In the tests given herein the alloy was prepared as follows:

Weighed quantities of the three metals (sodium, potassium, and lead) were introduced into an iron bomb, under an atmosphere of nitrogen. The bomb was sealed, then heated slowly to 450 C., a temperature sufilciently above the melting point of the alloy formed from the combination of the 3 metals to insure complete mixing and alloying. The alloy was mixed at this temperature for 10 minutes, at which time the contents of the bomb were rapidly solidified by directing a. rapid stream of cold water upon the outer surface of the bomb. By this means the solidification time of the alloy mass was between 1 and 5 seconds. The alloy was then removed from the bomb in a nitrogen atmosphere and comminuted to a convenient size for studying in subsequent reactions.

Similar tests have been made with equally good results using an alloy which was cooled very slowly during the solidification period, so that the crystallization time was very long (30-60 minutes).

However, our alloy can be prepared by any of the means found useful for preparing our present alloy. For example other methods can be employed as follows:

Conventional means employed in the present commercial process, wherein the alloy is cooled slowly upon vibrating bed casters.

- Drum-type castings, wherein the alloy is very rapidly crystallized upon the cold surface of a drum which rotates beneath the surface of the melted alloy.

By dropping or spraying the molten alloy into a cooled chamber, or into a cold liquid, such as a hydrocarbon or ethyl chloride.

Other examples and modifications of our invention can be made based on the above teachings and coming within the following claims.

We claim:

1. A process for making tetraethyllead comprising reacting ethyl chloride with a ternary alloy of sodium, potassium and lead, in which the sodium content is between 5 and 35 weight per cent and the potassium content is between 0.1 and 5 weight per cent, in the presence of an organic lead alkylating catalyst selected from the group consisting of organic oxygen-containing and nitrogen-containing materials, at a temperature below about C., under a pressure such that at the temperature used the ethyl chloride is maintained in the liquid phase, and for a time less than about 8 hours.

2. The process of claim 1 in which the total content of the alkali metal is between 48 and 52 atom per cent.

3. The process of claim 1 in which the amount of potassium is between 1 and 2 per cent and the atomic ratio of lead to total alkali metals is in the range of 1 to 1.

4. A process for making tetraethyllead comprising reacting ethyl chloride with a ternary alloy of sodium, potassium and lead in which the potassium content is between 1 and 2 weight per cent, the total sodium and potassium content is between 48 and 52 atom per cent in the presence of an acetone catalyst, at a temperature between 60 and 100 0., under a pressure such that at the temperature used the ethyl chloride is maintained in the liquid phase, and for a time between A and 8 hours.

5. A process for making tetraethyllead comprising reacting ethyl chloride with a ternary alloy of sodium, potassium and lead in which the sodium content is between 5 and 35 weight per cent and the potassium content is between 0.1 and 5 weight per cent, under a pressure such that at the temperature used the ethyl chloride is maintained in the liquid phase, and for a time less than 8 hours, and in the presence of a lead alkylating catalyst.

6. The process of claim 5 further defined in that the catalyst is a ketone.

7. The process of claim 5 further defined in that the catalyst is acetone.

8. The process of claim 5 further defined in that the catalyst is methyl ethyl ketone.

14. The process of claim 5 further defined in that the catalyst is acetaldehyde.

HYMIN SHAPIRO. EARL G. DE WITT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,664,021 Calcott et al. Mar. 27, 1928 1,717,961 Daudt et al. June 18, 1929 1,749,567 Daudt Mar. 4, 1930 1,962,173 Calcott et al June 12, 1934 2,464,397 Holbrook Mar. 15, 1949 2,464,399 Jackson Mar. 15, 1949 

5. A PROCESS FOR MAKING TETRAETHYLLEAD COMPRISING REACTING ETHYL CHLORIDE WITH A TERNARY ALLOY OF SODIUM, POTASSIUM AND LEAD IN WHICH THE SODIUM CONTENT IS BETWEEN 5 AND 35 WEIGHT PER CENT AND THE POTASSIUM CONTENT IS BETWEEN 0.1 AND 5 WEIGHT PER CENT, UNDER A PRESSURE SUCH THAT AT THE TEMPERATURE USED THE ETHYL CHLORIDE IS MAINTAINED IN THE LIQUID PHASE, AND FOR A TIME LESS THAN 8 HOURS, AND IN THE PRESENCE OF A LEAD ALKYLATING CATALYST. 